Cut the turkey breast fillet into small strips and the mushrooms into slices. Brown the meat in a pan, add the mushrooms and brown them briefly. Then place in a small bowl and set aside.
Cook pasta or spaetzle as usual.
Finely dice the onion and melt the butter in the saucepan. Then sweat the onions in it. Add the flour and stir vigorously. Roast a little and add the vegetable stock while stirring constantly. Add the meat and mushrooms and stir in the cream. Bring to the boil and add a little more stock or water if necessary. Season to taste with salt and pepper.